This project is designed to provide some insight into the pathophysiology, diagnosis, and treatment of acute osteomyelitis; the treatment of chronic osteomyelitis; and the treatment of the infected total hip arthroplasty. The initial phase of this project will address the treatment of chronic osteomyelitis with a local muscle flap. The goal of this phase is two-fold: 1) to document the usefulness of non-invasive examinations with dynamic 99m technetium scintigraphy and magnetic resonance imaging in the diagnosis and monitoring of therapy; and 2) to determine if parenteral antibiotic therapy can be reduced from four to two weeks with the use of a muscle flap. The second phase of this project will delve into the pathophysiology, diagnosis, and treatment of acute osteomyelitis in immature osseous tissue. Three non-invasive techniques - dynamic 99m technetium scintigraphy, magnetic resonance imaging, and 111 indium leukocyte imaging - will be compared in the diagnosis of acute osteomyelitis. Histological evaluation of the phagocytic capabilities of tissue based macrophages in the ascending and descending capillary loops of the growth plate will be analyzed with gram-stains of tissue, immunofluorescence, and electron microscopy of the tissue. The timing and duration of antibiotic therapy will be studied. The final phase of this project will compare "one-stage" exchange arthroplasty utilizing gentamicin impregnated acrylic cement with delayed reconstruction utilizing an ingrowth implant.